Marine Fossils and their Living Relatives

SALMONFossil: SalmonOncorhynchus new species

One million years ago, during the last Ice Age, adult salmon returned from the ocean and swam up a river in northwestern Washington to spawn in the waters where they had hatched four years before. Suddenly the river was blocked by ice, trapping the salmon in the lake that formed behind the ice dam. As the fish died, their bodies sank to the bottom of the lake where it was too cold or lacking in oxygen for scavengers to disturb their skeletons.

The fossil skeletons found in this ancient lake bed are almost complete and have skull features that resemble both sockeye and pink salmon. The fossils show that these large salmon, both male and female, were in their spawning stage.

Sockeye salmon are unique among Pacific salmon in that they nearly always spawn in streams connected to large lakes. On the west coast of the Olympic Peninsula a unique stock of sockeye salmon spawns in Lake Ozette. This small population is genetically distinct from other Pacific sockeye, remaining an additional year at sea before returning to spawn. In the 1990s fisheries managers saw their numbers declining, and in 1999 Lake Ozette sockeye were listed as threatened under the Endangered Species Act. Although they are no longer harvested, Lake Ozette sockeye are still sensitive to a variety of stresses and remain a species of concern.

The best place to see the fall migration of sockeye salmon in Puget Sound is at the Ballard locks. Visitors can watch through underwater windows as sockeye navigate the fish ladders around the locks on their way to streams flowing into Lake Washington.